Tire building drum and tire building method

ABSTRACT

Tire building drum and tire building method, capable of assembling tire component members with high accuracy. A tire building drum is used, which includes at least one core body, which is disposed at an axial inside of a pair of bead lock means, and which comprises a plurality of sheets of rigid support members disposed in a toroidal shape and adapted to be displaced and thereby expanded or contracted. Bead cores are locked by the bead lock means, respectively, and a center portion of a carcass band is bulged while displacing the bead lock means close to each other. Back side portions of the carcass band are folded to radial outsides around the bead cores, respectively. The core body is then radially expanded to the maximum diameter while locking the bead cores, and tire component members are assembled onto the radially expanded core body.

TECHNICAL FIELD

The present invention relates to a tire building drum and a tirebuilding method for conducting a tire building process from a carcassband up to formation of green tire on the same building drum, andparticularly to those for molding a tire with high accuracy.

BACKGROUND ART

In molding a green tire, there has been conventionally conducted amethod comprising the steps of: providing a cylindrical carcass band orgreen case on a shaping drum; bulging a center portion of the carcassband or green case into a toroidal shape; and uniting it to a belt/treadband established by bonding tire component members such as a belt memberand a tread rubber separately on a belt/tread forming drum.

However, in such a conventional method, the belt/tread band is oncedetached from the belt/tread forming drum, gripped from radiallyoutside, moved to the shaping drum, and this gripping is released thereso as to move the belt/tread band onto the shaping drum, with the resultthat the steps are made complicated and the tread band is gripped andreleased many times, thereby causing a problem of a deterioratedaccuracy of relative positions between the carcass band or green caseand the belt/tread band. To deal with it, there has been proposed amethod for directly assembling tire component members to a carcass bandon a building drum, as disclosed in JP-2002-326288A.

The above proposal is capable of solving the complexity of steps.However, in assembling tire component members, side portions of acarcass band are once folded back to radial outsides around bead cores,respectively, a center portion of the toroidally bulged carcass band isthen supported from a radial inside by a core device in a state wherethe bead cores are not locked to a building drum, and tire componentmembers are assembled onto the core device. This fails to attain arelative positional relationship between the assembled tire componentmembers and bead cores with high accuracy, thereby still failing tosolve the above problem in this point.

The present invention has been conceived in view of such a problem, andit is therefore an object of the present invention to provide a tirebuilding drum and a tire building method capable of assembling tirecomponent members directly onto a building drum having a carcass bandprovided thereon and capable of assembling the tire component memberswith high precision, in molding a tire by folding back side portions ofthe carcass band to radial outsides around bead cores, respectively.

DISCLOSURE OF INVENTION

The present invention has been carried out to achieve the above object,and its basic configurations and functions will be described below.

(1) The present invention provides a tire building drum comprising: apair of bead lock means which are axially displaceable toward and awayfrom each other for radial expansion or contraction; carcass bandfolding-back means, positioned adjacent to the bead lock means,respectively; and a center shaft for supporting these means;

wherein the tire building drum further comprises at least one core bodyat an axial inside of the bead lock means, the core body comprising aplurality of sheets of rigid support members which are toroidallydisposed and axially displaceable for radial expansion or contraction.

With such a tire building drum, the core body comprising the pluralityof sheets of rigid support members is provided so that tire componentmembers such as a belt member, tread rubber, sidewall rubbers and thelike can be precisely assembled based on the core body upon assemblingthese component members onto an outside of the bulged carcass bandcenter portion, and the core body is provided to be positioned on thecenter shaft of the same building drum relative to the pair of bead lockmeans so that bonding precision of the component members relative to thebead cores positioned by the bead lock means can be enhanced to therebyallow a tire to be built with high precision.

(2) The present invention further provides a tire building drumaccording to the item (1), further comprising: a center bladder adaptedto be axially deformed for radial expansion or contraction, whichextends at a radial outside of the core body, and which has both axialside portions adapted to be displaced toward and away from each otherintegrally with the bead lock means, respectively;

wherein the rigid support members are provided with comb tooth portions,respectively, for engagement of the rigid support members with eachother.

With such a tire building drum, the center bladder is provided so thatgaps between the rigid support members at an outer peripheral surfacedefined by these rigid support members upon radially expanding the rigidsupport members are covered by the center bladder deformable for radialexpansion or contraction to thereby enable a carcass band center portionto be uniformly supported and to thereby enable a bonding surface to besmoothened and uniformalized upon bonding the belt member thereto, andthe rigid support members are engaged with each other by the functionsof the respective comb tooth portions thereby allowing formation ofhighly precise bonding surface.

(3) The present invention further provides a tire building drumaccording to the item (1) or (2), wherein the bead lock means eachcomprise: bead lock segments circumferentially arranged adjacent to eachother so as to be expanded or contracted in an annular shape; associatedlinks having one ends hinged to the bead lock segments, respectively;bead lock pistons coupled to other ends of the links, respectively, andprovided in axially displaceable manner; and bead lock cylinders adaptedto displace the associated bead lock pistons, respectively.

With such a tire building drum, the bead lock pistons are axiallydisplaced to thereby allow all the bead lock segments in the annularshapes to be displaced for radial expansion or contraction to uniformlyretain the bead cores over the entire circumferences thereof,respectively, and the bead lock pistons are driven by the internal beadlock cylinders so that the building drum can be constituted compactly.

(4) The present invention also provides a tire building drum accordingto the item (3), further comprising: means for varying an axial positionof that bead lock means relative to an axial side portion of the centerbladder, which is located at the same axial side as the axial sideportion of the center bladder.

With such a tire building drum, the axial position of the bead lockmeans is brought outwardly, to thereby allow a clearance to be ensuredat the axial outside of the center bladder for detaching an associatedbladder ring for latching an associated edge portion of the centerbladder, thereby resultingly facilitating an exchanging operation of thecenter bladder.

(5) The present invention further provides a tire building drumaccording to any one of the items (1) through (4), wherein the carcassband folding-back means are adapted to be displaced toward and away fromeach other, integrally with the bead lock means at the axially samesides as the carcass band folding-back means, respectively; and

wherein each of the carcass band folding-back means includes: aplurality of folding-back arms arranged in a circumferential directionand having tip end portions at axial insides, respectively; neck-turningmembers hinged to the tip end portions of the folding-back arms,respectively, so as to be swung to radial inside and outside;folding-back rollers circumferentially extending and born bylongitudinal opposite end portions of the associated neck-turningmembers, respectively; a slide ring hinged to proximal ends of theplurality of folding-back arms and adapted to be displaceable to axialinside and outside relative to the associated bead lock means; andurging means for exerting a swinging force directed toward a radialinside, onto the folding-back arms.

With such a tire building drum, the folding-back rollers born by thelongitudinal opposite end portions of the neck-turning members swingablycoupled to the tip end portions of the folding-back arms can be rolledlycontacted with the carcass band side portions to thereby fold back them,respectively, so that the swinging forces by the urging means can beconverted into uniform urging forces to the carcass band center portionto thereby allow the carcass band side portions to be uniformlypressure-jointed to the carcass band center portion.

(6) The present invention further provides a tire building drumaccording to the item (5), wherein each of a pair of the folding-backrollers born by the associated neck-turning member is divided into twoportions at both sides of an associated portion of the neck-turningmember for supporting the folding-back roller, and is circumferentiallyprotruded from the associated neck-turning member, so that protrudeddirections of the pair of folding-back rollers are opposite to eachother, and so that a roller rotational shaft supporting portioncorresponding to one of the pair of folding-back rollers has acircumferentially extended area positioned within a circumferentiallyextended area of the other folding-back roller.

With such a tire building drum, the folding-back rollers mounted onopposite ends of the associated neck-turning members arecircumferentially oppositely protruded from the associated neck-turningmembers, respectively, i.e., these rollers are mounted on the associatedarm in an offset manner, so that the roller of one folding-back armprotruded between neighboring folding-back arms does not interfere withthe roller of another arm even when tip end portions of the folding-backarms are radially contracted and thus the neighboring tip end portionsare narrowed in spacing, thereby allowing spacings between neighboringarms to be minimized, and in this way, the folding-back arms can bedensely arranged in the circumferential direction while eliminating sucha region of the carcass band side portion which is not pressure-jointedby any of the paired folding-back rollers in a state where the tip endportions of the folding-back arms are radially expanded, therebyenabling strong adhesion between the carcass band center portion and thecarcass band side portion and enabling prevention of a relativedisplacement therebetween.

Further, the folding-back rollers at opposite ends of each neck-turningmember are each divided into two portions at both sides of thoseportions of the neck-turning member which support the roller shafts forthe rollers, respectively, thereby enabling prevention of a fact that:that portion of the carcass band side portion which is stretched towarda radial outside between neighboring rollers during folding back, isabutted on the non-rotating supporting portion and thus the carcass bandside portion is damaged.

(7) The present invention further provides a tire building drumaccording to the item (5) or (6), wherein each of the folding-backrollers is provided with roller rotational speed restricting means forrestricting a roller rotational speed correspondingly to this speed.

Since a folding back resistance is large at an initial stage of foldingback and a folding back resistance is small at a final stage of foldingback in folding back the carcass band side portion by the folding-backmeans, the speed of the tip end of each arm, i.e., the rotational speedsof the associated rollers are increased at those portions of the carcassband side portion where the folding back resistance is small therebyshortening a time where the rollers stay on the carcass band sideportion per unit length thereof, thereby possibly causing a problem thatthe carcass band side portion is not sufficiently pressure-jointed.However, according to this tire building drum, there is provided theroller rotational speed restricting means for restricting the rollerrotational speed correspondingly to this speed, thereby enablingprevention of this problem.

(8) The present invention further provides a tire building drumaccording to any one of the items (1) through (7), wherein the core bodyis provided by one in number and arranged in-between the pair of beadlock means; and

wherein the tire building drum further comprises: a pair of sleevesadapted to be displaced toward and away from each other on the centershaft; sleeve reciprocative driving means for displacing the sleeves;and link mechanisms having one ends coupled to the rigid supportmembers, respectively, and the other ends coupled to the pair ofsleeves, respectively, the link mechanisms being each adapted with apair of links having intermediate portions hinged to each other,respectively.

With such a tire building drum, the rigid support members are displacedand radially expanded or contracted by the pair of sleeves to bedisplaced away from or close to each other and by the link mechanismscoupled to the sleeves, respectively, so that axial center positions ofthe rigid support members are precisely kept unchanged and even beforeand after expansion or contraction, and further, the core body isprovided by one in number so that the core body is adapted to supportthe carcass band over a full width thereby allowing a solid bondingsurface for tire component members.

(9) The present invention further provides a tire building drumaccording to the item (8), wherein the sleeve reciprocative drivingmeans is adapted with: screw portions formed at end portions of thesleeves, respectively, and having mutually opposite lead orientationsfor the right and left sleeves, respectively; screw blocks threadedlyengaged with the screw portions, respectively; and rotating means forrelatively rotating the sleeves and the associated screw blocks,respectively;

wherein the tire building drum further comprises: sliders having mountedthereon the bead lock means, respectively, and adapted to displace thebead lock means toward and away from each other; and bead lockreciprocative driving means for displacing the pair of bead lock means;and

wherein the bead lock reciprocative driving means is adapted with:female screw members coupled to radial insides of the sliders,respectively; a screw shaft disposed in a hollow of the center shaft andhaving right and left male screw portions threadedly engaged with theassociated female screw members, respectively; and screw shaft rotatingmeans for rotating the screw shaft; in which the right and left malescrew portions of the screw shaft have mutually opposite leadorientations, respectively.

With such a tire building drum, the sleeve reciprocative driving meansis adapted with the oppositely oriented screw portions formed on thesleeves, respectively, and with the screw blocks threadedly engaged withthe screw portions, respectively, so that the pair of sleeves can bedisplaced close to and away from each other precisely and intendedly,and so that the rigid support members to be expanded or contracted bydisplacement of the sleeves can be easily, rapidly displaced to beexpanded or contracted and positioned to predetermined radial positionsof the building drum with high precision in conformity to a size of tireto be molded, with a simple mechanism; and the bead lock reciprocativedriving means is adapted with the female screw members coupled to thesliders, respectively, and the screw shaft disposed in the hollow of thecenter shaft and having right and left male screw portions threadedlyengaged with the associated female screw members, respectively, so thatthe axial center positions of the bead lock means can be held with highaccuracy while allowing the right and left bead lock means to bedisplaced to each other to a predetermined spacing and to be preciselypositioned, with a compact mechanism.

(10) The present invention also provides a tire building drum accordingto the item (8), further comprising: means for restraining rotation ofthe screw blocks; and means for rotating, together with the sleeves, thecenter shaft fitted through the sleeves by circumferential convex andconcave.

With such a tire building drum, the center shaft is rotated in a statewhere the screw blocks are fixed by the rotation restraining means forthe screw blocks, so that the sleeves can be rotated integrally with thecenter shaft under operation of concave and convex fitting portionswhile the screw portions provided on the sleeves axially displaceablerelative to the center shaft can be rotated synchronizedly with eachother relative to the screw blocks, respectively, thereby enabling bothsleeves to be displaced close to or away from each other by distancescorresponding to a rotated amount of the center shaft in relation toscrew pitches of the screw portions.

(11) The present invention also provides a tire building drum accordingto the item (9), further comprising: means for rotating both the screwblocks synchronizedly with each other; and means for fitting the sleevesonto the center shaft by circumferential convex and concave.

With such a tire building drum, the screw blocks are rotatedsynchronizedly with each other, thereby allowing the pair of sleeves tobe displaced close to or away from each other by distances correspondingto rotated amounts of the screw blocks, respectively.

(12) The present invention also provides a tire building drum accordingto the item (10) or (11), further comprising: means for restrictingrotation of the screw blocks relative to the center shaft.

With such a tire building drum, after both sleeves are displaced closeto or away from each other, there is released restraint of the rotationrestraining means for the screw blocks, if any, and the means forrestricting rotation of the screw blocks relative to the center shaft isoperated, thereby allowing the positions of the screw blocks relative tothe center shaft to be kept constant, so that the positions of thesleeves concave and convex fitted to the center shaft relative to thescrew blocks are kept constant, and thus positions of the pair ofsleeves relative to each other in an axial direction can be keptconstant.

(13) The present invention further provides a tire building drumaccording to the item (8), wherein the sleeve reciprocative drivingmeans is adapted with: female screw members coupled to the sleeves atradial insides thereof, respectively; a screw shaft disposed in a hollowof the center shaft and having right and left male screw portionsthreadedly engaged with the associated female screw members,respectively; and screw shaft rotating means for rotating the screwshaft; in which the right and left male screw portions of the screwshaft have mutually opposite lead orientations, respectively;

wherein the tire building drum further comprises: sliders having mountedthereon the bead lock means, respectively, and adapted to displace thebead lock means toward and away from each other; and bead lockreciprocative driving means for displacing the pair of bead lock means;and

wherein the bead lock reciprocative driving means is adapted with: screwportions formed at end portions of the sliders, respectively, so as tohave mutually opposite screw thread extending directions for the rightand left sliders, respectively; screw blocks threadedly engaged with thescrew portions, respectively; and rotating means for rotating thesliders and the screw blocks relative to each other.

With such a tire building drum, the sleeve reciprocative driving meansis adapted with: female screw members coupled to the sleeves at radialinsides thereof, respectively; a screw shaft disposed in a hollow of thecenter shaft and having right and left male screw portions threadedlyengaged with the associated female screw members, respectively, so thatthe pair of sleeves can be displaced close to and away from each otherprecisely and intendedly, and so that the rigid support members to beexpanded or contracted by displacement of the sleeves can be easily,rapidly displaced to be expanded or contracted and positioned topredetermined radial positions of the building drum with high precisionin conformity to a size of tire to be molded, with a compact mechanism;and the bead lock reciprocative driving means is adapted with theoppositely oriented screw portions formed at the sliders, respectively,and the screw blocks threadedly engaged with the screw portions,respectively, so that the axial center positions of the bead lock meanscan be held with high accuracy while allowing the right and left beadlock means to be displaced to each other to a predetermined spacing andto be precisely positioned, with a simple mechanism.

(14) The present invention also provides a tire building drum accordingto the item (13), further comprising: means for restraining rotation ofthe screw blocks; and means for rotating, together with the sliders, thecenter shaft fitted through the sliders by circumferential convex andconcave.

With such a tire building drum, the center shaft is rotated in a statewhere the screw blocks are fixed by the rotation restraining means forthe screw blocks, so that the sliders can be rotated integrally with thecenter shaft under operation of concave and convex fitting portionswhile the screw portions provided on the sliders axially displaceablerelative to the center shaft can be rotated synchronizedly with eachother relative to the screw blocks, respectively, thereby enabling bothsliders to be displaced close to or away from each other by distancescorresponding to a rotated amount of the center shaft in relation toscrew pitches of the screw portions.

(15) The present invention also provides a tire building drum accordingto the item (13), further comprising: means for rotating both the screwblocks synchronizedly with each other; and means for fitting the slidersonto the center shaft by circumferential convex and concave.

With such a tire building drum, the screw blocks are rotatedsynchronizedly with each other, thereby allowing the pair of sliders tobe displaced close to or away from each other by distances correspondingto rotated amounts of the screw blocks, respectively.

(16) The present invention also provides a tire building drum accordingto the item (14) or (15), further comprising: means for restrictingrotation of the screw blocks relative to the center shaft.

With such a tire building drum, after both sliders are displaced closeto or away from each other, there is released restraint of the rotationrestraining means for the screw blocks, if any, and the means forrestricting rotation of the screw blocks relative to the center shaft isoperated, thereby allowing the positions of the screw blocks relative tothe center shaft to be kept constant, so that the positions of thesliders concave and convex fitted to the center shaft relative to thescrew blocks are kept constant, and thus positions of the pair ofsliders relative to each other in an axial direction can be keptconstant.

(17) The present invention further provides a tire building drumaccording to any one of the items (1) through (7), wherein the corebodies are provided by two in number, and the core bodies are arrangednear axial insides of the pair of bead lock means, respectively;

wherein the tire building drum further comprises: a pair of slidershaving mounted thereon the core bodies and the bead lock means locatedat the axially same sides as the sliders, respectively; sliderreciprocative driving means for displacing the sliders, respectively;and core-body expanding/contracting means for expanding or contractingthe core bodies, respectively; and

wherein each of the core-body expanding/contracting means is adaptedwith: expanding/contracting link parts coupled to the rigid supportmembers constituting the associated core body, respectively; a screwblock restrained in axial displacement and adapted to be rotatablerelative to the center shaft; a longitudinal movement screw memberthreadedly engaged with the screw block so as to be restrained inrotation about the center shaft, and adapted to be axially displaceable;and a link uniting part for coupling the expanding/contracting linkparts to the longitudinal movement screw member.

With such a tire building drum, each of the core-bodyexpanding/contracting means is constituted in the above manner, so thataxial center positions of the rigid support members are unchangedprecisely and even before and after expansion or contraction, andfurther, the core bodies are provided by two in number adapted withright and left ones so that tires having different widths can be moldedon the same building drum by simply varying a distance between the corebodies, thereby allowing laborious work for exchanging building drums tobe omitted upon producing various sizes of tires having differentwidths, respectively.

(18) The present invention further provides a tire building drumaccording to the item (17), wherein the slider reciprocative drivingmeans are adapted with: female screw members coupled to the sliders atradial insides thereof, respectively; a screw shaft disposed in a hollowof the center shaft and having right and left male screw portionsthreadedly engaged with the female screw members, respectively; andscrew shaft rotating means for rotating the screw shaft; in which theright and left male screw portions of the screw shaft have mutuallyopposite leads, respectively.

With such a tire building drum, the slider reciprocative driving meansare adapted with: female screw members coupled to the sliders,respectively; and the screw shaft disposed in a hollow of the centershaft and having right and left male screw portions threadedly engagedwith the female screw members, respectively; so that the axial centerpositions of the bead lock means and the core bodies can be held withhigh accuracy while allowing the right and left bead lock means and thecore bodies to be displaced to each other to predetermined spacings andto be precisely positioned, respectively, with a compact mechanism.

(19) The present invention also provides a tire building drum accordingto the item (17) or (18), further comprising: means for restrainingrotation of the screw blocks; and means for rotating, together with thesliders, the center shaft fitted through the sliders by circumferentialconvex and concave.

With such a tire building drum, the center shaft is rotated in a statewhere the screw blocks are fixed by the rotation restraining means forthe screw blocks, so that the sliders can be rotated integrally with thecenter shaft under operation of concave and convex fitting portionswhile the screw portions provided on the sliders axially displaceablerelative to the center shaft can be rotated synchronizedly with eachother relative to the screw blocks, respectively, thereby enabling bothsliders to be displaced close to or away from each other by distancescorresponding to a rotated amount of the center shaft in relation toscrew pitches of the screw portions.

(20) The present invention also provides a tire building drum accordingto the item (17) or (18), further comprising: means for rotating boththe right and left screw blocks synchronizedly with each other; andmeans for fitting the sliders onto the center shaft by circumferentialconvex and concave.

With such a tire building drum, the screw blocks are rotatedsynchronizedly with each other, thereby allowing the pair of sliders tobe displaced close to or away from each other by distances correspondingto rotated amounts of the screw blocks, respectively.

(21) The present invention also provides a tire building drum accordingto the item (19) or (20), further comprising: means for restrictingrotation of the screw blocks relative to the center shaft.

With such a tire building drum, after both sliders are displaced closeto or away from each other, there is released restraint of the rotationrestraining means for the screw blocks, if any, and the means forrestricting rotation of the screw blocks relative to the center shaft isoperated, thereby allowing the positions of the screw blocks relative tothe center shaft to be kept constant, so that the positions of thesliders concave and convex fitted to the center shaft relative to thescrew blocks are kept constant, and thus positions of the pair ofsliders relative to each other in an axial direction can be keptconstant.

(22) The present invention further provides a tire building method usingthe tire building drum of any one of the items (1) through (21),comprising steps of:

locking bead cores by the bead lock means, respectively;

then bulging a center portion of a carcass band while displacing thebead lock means close to each other;

folding back side portions of the carcass band to radial outsides aroundthe bead cores, respectively;

thereafter radially expanding the core body to a maximum diameter, whilelocking the bead cores; and

assembling tire component members onto the radially expanded core body.

With such a tire building method, upon assembling tire component memberssuch as a belt member, tread rubber, sidewall rubbers and the like ontoan outside of a bulged carcass band center portion, these componentmembers are directly assembled on a building drum having previouslyarranged thereon the carcass band while locking the bead cores in amanner that these tire component members are assembled based on the corebody, thereby enabling precise assembling of the tire component members,with high precision in positions of the tire component members relativeto both bead cores. It is noted that the carcass band here means acombination of tire component members including a carcass memberlaminated into a band shape.

(23) The present invention further provides a tire building method usingthe tire building drum according to any one of the items (5) through(21), comprising a step of:

moving the folding-back arms of the folding-back means to axial insidessynchronizedly with each other, respectively, to synchronizingly swingto radial outsides the folding-back arms around proximal ends thereofagainst swinging forces by the urging means while causing thefolding-back rollers to be rolledly contacted with carcass band sideportions, respectively, to thereby fold back the carcass band around thebead cores.

With such a tire building method, folding back is conducted by movingthe folding-back arms to the axial insides synchronizedly with eachother, so that folding back can be uniformly conducted over an entirecircumference, and by virtue of the urging means, carcass band sideportions can be pressure-jointed to a carcass band center portion at asufficient strength.

(24) The present invention further provides a tire building methodaccording to the item (23), wherein the folding-back arms aresynchronizedly swung to radial outsides, respectively, such that sideportions of the carcass band to be folded back by the folding-back meansare rolledly pressure-jointed to a carcass band center portion by anyone of the folding-back rollers at any point of the side portions of thecarcass band.

With such a tire building method, side portions of the carcass band arepressure-jointed to a carcass band center portion by any one of thefolding-back rollers at any point of the side portions of the carcassband, so that close contact of the carcass band side portions with thecarcass band center portion is ensured to avoid relative displacementbetween them during tire production, thereby achieving high dimensionalprecision of a tire.

(25) The present invention also provides a tire building method usingthe tire building drum according to any one of the items (8) through(16), further comprising a step of: radially expanding the core body toa position where at least side surfaces of the core body are opposed tothe bead cores, respectively, and then folding back the carcass bandside portions around the bead cores, respectively.

With such a tire building method, bead cores and tire portionstherearound can be supported from axial insides thereof by the sidesurfaces of the core body having high rigidity, so that carcass bandside portions can be tightly folded back around bead cores, therebyenabling molding of a tire having an excellent bead firmness.

(26) The present invention also provides a tire building methodaccording to the item (25), further comprising a step of: radiallyexpanding the core body to a position where side surfaces of the corebody are opposed to the bead cores, respectively, and thereafterdisplacing the bead lock means to an axial center to bring the bead lockmeans close to core body side surfaces, respectively, thereby startingfolding back of the carcass band side portions.

With such a tire building method, the core body is radially expanded toa position where side surfaces of the core body are opposed to the beadcores, respectively, and thereafter the bead lock parts are moved to anaxial center, so that spacings between the bead lock parts and the corebody can be minimized, thereby allowing the bead cores to be moreassuredly supported by the side surfaces of the core body.

(27) The present invention also provides a tire building methodaccording to the item (26), further comprising a step of: folding backthe carcass band side portions by the folding-back rollers while urgingthe carcass band side portions toward the carcass band center portionsupported by core body side portions.

With such a tire building method, the carcass band side portions arefolded back by the folding-back rollers while urging the carcass bandside portions toward the carcass band center portion supported by corebody side portions, so that close contact of the carcass band sideportions with the carcass band center portion is ensured to therebyattain high dimensional precision of a tire.

(28) The present invention also provides a tire building methodaccording to any one of the items (25) through (27), further comprisinga step, after folding back the carcass band side portions around thebead cores, respectively, of pressure-jointing folded back end portionsby stitching rollers each subjected to a knurling treatment.

With such a tire building method, the folded back ends arepressure-jointed by the stitching rollers each subjected to a knurlingtreatment, so that occurrence of separation from the tire folded backends can be assuredly prevented.

(29) The present invention also provides a tire building methodaccording to any one of the items (25) through (28), further comprisinga step of: gradually reducing a pressure within the center bladder, asan interior of the center bladder is pressurized to bulge a centerportion of the carcass band and as the core body is radially expanded toa maximum diameter.

With such a tire building method, the core body is radially expanded tothe maximum diameter while gradually reducing the pressure within thebladder, so that the core body can be radially expanded smoothly thoughradial expansion of the core body was difficult if such a pressurereduction was not conducted.

(30) The present invention also provides a tire building methodaccording to any one of the items (25) through (29), further comprisingsteps of:

detecting a load of a motor for driving the sleeve reciprocative drivingmeans upon radially expanding the core body; and

controlling at least one of an internal pressure of the center bladder,and a spacing between the pair of bead lock means, based on a value ofthe load.

With such a tire building method, there is controlled an internalpressure of the center bladder or a spacing between the right and leftbead lock means by detecting a load of the motor for driving the sleevereciprocative driving means as a property alternative to a resistanceforce upon radially expanding the core body, thereby allowing a smoothradial expansion of the core body to be further ensured.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a tire building drum according to afirst embodiment of the present invention.

FIG. 2 is a view showing the manner of radial expansion or contractionof a core body and links.

FIG. 3 is a cross-sectional view of an example of reciprocative drivingmeans for a sleeve.

FIG. 4 is a cross-sectional view of another embodiment of reciprocativedriving means for the sleeve.

FIG. 5 is a front view of a tip end portion of a folding-back arm offolding-back means.

FIG. 6 is an axial side view of the folding-back arms.

FIG. 7 is a cross-sectional view of roller rotational speed restrictingmeans.

FIG. 8 is a cross-sectional view of a tire in course of molding,illustrating a tire building process corresponding to the firstembodiment.

FIG. 9 is a cross-sectional view of the tire in course of molding,illustrating another molding step subsequent to FIG. 8.

FIG. 10 is a cross-sectional view of the tire in course of molding,illustrating a further molding step subsequent to FIG. 9.

FIG. 11 is a cross-sectional view of the tire in course of molding,illustrating still another molding step subsequent to FIG. 10.

FIG. 12 is a cross-sectional view of a tire building drum according to asecond embodiment of the present invention.

FIG. 13 is a cross-sectional view of a tire building drum according to athird embodiment of the present invention.

FIG. 14 is a detailed partial cross-sectional view of the tire buildingdrum of the third embodiment.

FIG. 15 is another detailed partial cross-sectional view of the tirebuilding drum of the third embodiment.

FIG. 16 is a further detailed partial cross-sectional view of the tirebuilding drum of the third embodiment.

FIG. 17 is a still another detailed partial cross-sectional view of thetire building drum of the third embodiment.

FIG. 18 is a diagrammatic arrangement view illustrating interconnectionbetween the tire building drum and a molding machine.

FIG. 19 is a partially cut-away diagrammatic view of the building drumof the third embodiment illustrating a molding procedure thereof.

FIG. 20 is a partially cut-away diagrammatic view of the building drumof the third embodiment illustrating another molding procedure thereofsubsequent to FIG. 19.

FIG. 21 is a partially cut-away diagrammatic view of the building drumof the third embodiment illustrating a further molding procedure thereofsubsequent to FIG. 20.

FIG. 22 is a cross-sectional view of screw shaft origin posture holdingmeans.

BEST MODE FOR CARRYING OUT THE INVENTION

There will be explained embodiments of the present invention withreference to the accompanying drawings. FIG. 1 is a schematiccross-sectional view of substantially half of a tire building drumaccording to a first embodiment of the present invention, including acenter axis of the tire building drum.

This building drum 1 is provided with a pair of sleeves 3 to bedisplaced toward and away from each other in an axial direction on acenter shaft 2. Provided at an outer peripheral surface of each sleeve 3is an associated slider 4 to be displaced toward and away from eachother on a center axis of the associated sleeve 3 and independently ofthe sleeve 3. Fixedly provided on an outer periphery of each slider 4 isassociated bead lock means 7 for lockingly supporting an associated beadcore, and each bead lock means 7 comprises: bead lock segments 71 whichare circumferentially neighbored to each other to be expanded orcontracted in an annular shape; associated links 72 having one endshinged to the bead lock segments 71, respectively; bead lock pistons 73coupled to other ends of the links 72, respectively, and provided in anaxially displaceable manner; and bead lock cylinders 74 fixed on theouter periphery of the associated sleeve 3 and adapted to displace theassociated bead lock pistons 73, respectively.

Provided at an axial center between both bead lock means 7 is one corebody 10 to be expanded or contracted in a radial direction, and thiscore body 10 is adapted with a plurality of sheets of rigid supportmembers 10 a each in a semicylindrical shape and each having comb toothportions which are mutually engaged to establish a toroidal shape, in amanner that each rigid support member 10 a is coupled with one end of anassociated link mechanism 11 comprising a pair of links 11 a havingintermediate portions hinged to each other, and that other end portionsof each link mechanism 11 are mounted on the associated pair of sleeves3, respectively, while sleeve reciprocative driving means to bedescribed later are mounted on the pair of sleeves 3 for displacing thesame, respectively.

The building drum 1 further comprises: folding-back means 8 provided atthe right and left sliders 4, respectively; and a center bladder 9comprising a reinforced rubber membrane which extends to a radialoutside of the core body 10 to hermetically seal a space around the corebody 10 and which is deformed and thereby expanded or contracted in atoroidal manner; such that both axial side portions of the centerbladder 9 are fixed to axial inside ends of the sliders 4 at positionsaxially inside and near the bead lock means 7, respectively. Based onthis configuration, both axial side portions of the center bladder 9 aredisplaced toward and away from each other, integrally with the bead lockmeans 7 at the axially same sides as the both axial side portions of thecenter bladder 9, respectively.

FIG. 1 a shows a state where the core body 10 has been radiallyexpanded, and the pair of bead lock means 7 have been displaced close toeach other, and FIG. 1 b shows a state where the core body 10 has beenradially contracted and the bead lock means 7 have been displaced awayfrom each other.

To displace the paired bead lock means 7 close to each other, theassociated sliders 4 are displaced close to each other. Further, todisplace to radially expand the bead lock segments 71, the associatedbead lock pistons 73 are axially inwardly displaced to thereby radiallyexpand those end portions of the associated links 72 which are at thebead lock segments 71, respectively.

Here, bead lock reciprocative driving means for displacing the pairedbead lock means 7 close to each other, is adapted with: female screwmembers 41 coupled, through coupling members 42, to radial insides ofsliders 4 having bead lock means 7 installed thereon, respectively; ascrew shaft 50 disposed in a hollow of the center shaft 2 and havingright and left male screw portions 51 threadedly engaged with theassociated female screw members 41, respectively; and screw shaftrotating means (not shown) for rotating the screw shaft 50; in which theright and left male screw portions 51 of the screw shaft 50 havemutually opposite lead orientations, respectively. Based on thisconfiguration, the screw shaft 50 is rotated by the screw shaft rotatingmeans to displace the female screw members 41 toward and away from eachother in a left-right symmetric manner, thereby allowing the paired beadlock means 7 installed on the sliders 4 to be precisely displaced towardand away from each other. It is noted that the center shaft 2 andsleeves 3 are formed with elongated through-holes 2 a, 3 a,respectively, for allowing the coupling members 42 to penetratetherethrough, respectively.

In case of radially expanding the core body 10, the sleeves 3 aredisplaced close to each other by the associated reciprocative drivingmeans, respectively, to thereby displace end portions of each pair oflinks 11 a coupled to the sleeves 3, close to each other. Thus, that endportion of each link mechanism 11 which is located at the associatedrigid support member 10 a, is displaced to be radially expanded togetherwith the rigid support member 10 a and to be held in position.

FIG. 2 is a view showing the manner of a radial expansion or contractionof the core body 10 and link mechanisms 11, in which FIG. 2 a is aradial view of the core body 10 radially expanded to a maximum diameter,FIG. 2 b is a radial view of the core body 10 when radially contracted,and FIG. 2 c is an axial view of the core body. FIG. 2 c shows a stateradially expanded to the maximum diameter in a solid line, and aradially contracted state in a two-dot chain line. The rigid supportmembers 10 a constituting the core body 10 each include comb toothportions, are equidistantly arranged in a circumferential direction, andestablish such a structure that the opposing comb tooth portions ofneighboring rigid support members 10 a are engaged with each other,respectively. This enables a shaped carcass band to be supported byvirtue of rigidity of the rigid support members from an inside of thecenter bladder 9 over a range from a state radially expanded to themaximum diameter up to a radially contracted state, thereby allowing abelt member and a tread rubber to be precisely assembled onto an outerperiphery of the carcass band. Further, at a position during radialexpansion, side surfaces of the shaped carcass band can be supportedfrom an axial inside by virtue of rigidity of the side surface of therigid support members 10 a, thereby enabling carcass band side portionsto be assuredly pressure-jointed to tire component members includingbead cores upon folding back the carcass band side portions, so thatbead firmness is improved.

As shown in FIG. 1, reciprocative driving means for the sleeves 3 may beadapted with: screw portions 12 formed at end portions of the sleeves 3,respectively, and having mutually opposite screw thread extendingdirections for the right and left sleeves 3, respectively; screw blocks13 threadedly engaged with the screw portions, respectively; androtating means (not shown) for relatively rotating the sleeves 3 and theassociated screw blocks 13, respectively. In this case, provided at endportions of the center shaft 2 are stoppers 14 for restricting axialdisplacements of the screw portions 12 of sleeves 3, respectively.

Although the screw portions 12 and screw blocks 13 in FIG. 1 are adaptedwith male screws and female screws, respectively, reverse combinationsare possible.

In this way, there is adopted the screw mechanism which is simpler andhas high versatility so that the pair of sleeves 3 are preciselydisplaced close to and away from each other on the center shaft 2 of thetire building drum to thereby displace end portions of the pairs oflinks 11 a coupled to the associated sleeves 3, respectively, close toand away from each other, thereby enabling the rigid support members 10a to be displaced for expansion or contraction together with those endportions of the links 11 a which are located at the associated rigidsupport members 10 a, and as a result, the rigid support members 10 acan be held in arbitrary radial positions of the building drum 1 withhigh precision in conformity to a size of tire to be molded, therebyenabling assembling of belt member, tread rubber and the like with highprecision.

Preferably, as shown in FIG. 3 a, as rotation restraining means for eachscrew block 13, there are provided: a brake disks 15 disposed at anouter periphery of the screw block 13; a brake 16 disposed at an outerperiphery of the brake disk and having a base portion fixed to theground; a key 17 for fitting the sleeve 3 onto the center shaft 2 of thebuilding drum 1 in a relatively displaceable manner in an axialdirection; and means 18 such as a stepping motor for rotating the centershaft 2 and disposed at the end portion thereof. It is noted that splinefitting or serration fitting is possible instead of the key fitting.

Based on the above, the center shaft 2 is rotated in a state where screwblock 13 are fixed by the associated brakes 16 as the rotationrestraining means for the screw blocks 13, so that the sleeves 3 fittedby the key 17 onto the center shaft 2 in the relatively displaceablemanner in the axial direction are rotated relative to the right and leftfemale screw members 13, respectively, thereby enabling the pair ofsleeves 3 to be displaced close to or away from each other by distancescorresponding to a rotated amount of the center shaft 2.

More preferably, as shown in FIG. 3 b, there is provided a single-sidedbrake 19 adjacent to the associated screw block 13 and having a baseportion fixed to the center shaft end portion of the building drum 1. Inthis way, by releasing the brake 16 having the base portion fixed to theground and by operating the single-sided brake 19 having the baseportion fixed to the center shaft end portion of the building drum, theposition of the screw block 13 relative to the center shaft 2 can bekept constant, so that positions of the pair of sleeves 3 relative toeach other in an axial direction can be kept constant.

Alternatively, as shown in FIG. 4, the reciprocative driving means forthe sleeves 3 are adapted with: screw portions 12 formed at end portionsof the sleeves 3, respectively; screw blocks 13 threadedly engaged withthe screw portions, respectively; and means 20 comprising a combinationof stepping motor and gear mechanism, for example, for rotating thescrew blocks 13 in a synchronized manner; in which the sleeves 3 arefitted onto the center shaft 2 of the building drum 1 by a key 17 in arelatively displaceable manner in an axial direction. It is alsopossible here to employ spline fitting or serration fitting instead ofthe key fitting.

In this case, the screw blocks 13 are rotated synchronizedly with eachother so that the pair of sleeves 3 can be displaced close to or awayfrom each other by distances corresponding to rotated amounts of thescrew blocks 13, respectively.

Also by such a configuration, the pair of sleeves 3 are preciselydisplaced close to and away from each other on the center shaft 2 of thebuilding drum 1, thereby allowing the rigid support members 10 a to bepositioned at arbitrary radial positions of the building drum 1 withhigh precision in conformity to a tire size.

Here, the core body 10 is preferably and constantly mounted on thebuilding drum 1 except for a situation where the core body 10 is to bedisassembled and detached from the building drum for maintenance, forexample, such that it becomes unnecessary to take account of readinessupon detaching and attaching the core body 10 from and to the centershaft so that the sleeves 3 having the core body 10 mounted thereon andreciprocally displaced on the center shaft are allowed to maintain highpositional precision relative to the center shaft 2, and this results inthat positions of bead cores relative to the tread rubber, belt member,and the like to be formed on the core body 10 are made highly precise tothereby allow for molding of a highly precise tire as compared with abuilding drum adapted such that the core body 10 is detached from thecenter shaft 2 each time a tire is molded.

There will be now explained the configuration and operation of eachfolding-back means 8, with reference to FIG. 1, FIG. 5 illustratingdetails of a tip end portion of a folding-back arm 21 of a folding-backmeans 8 in a front view, and FIG. 6 illustrating the manner of radialexpansion or contraction of the folding-back arms 21 viewed from anaxial direction. It is noted that FIG. 5 illustrates a state in a solidline where a tip end of the folding-back arm 21 is radially contractedand a state in a two-dot chain line where the tip end is radiallyexpanded to an intermediate radius, and FIG. 6 illustrates a state in asolid line where tip ends of the folding-back arms 21 are radiallyexpanded and a state in a two-dot chain line where the tip ends areradially contracted.

Each folding-back means 8 comprises: a common slide ring 30 which is tobe axially and reciprocally displaced on a periphery of the associatedslider 4 and which has a displacement range to be defined by a stopper32 provided on the slider 4; folding-back arms 21 radially swingablymounted, through swing pins 37, on brackets 33 circumferentiallyequidistantly provided on an outer peripheral surface of the slide ring30, respectively, so as to be extended toward an axial inside;neck-turning members 22 hinged to tip end portions of the folding-backarms 21 through swing pins 25, respectively, so as to be swung in aradial direction; folding-back rollers 23, 24 to be rotated aroundshafts provided at longitudinal opposite end portions of theneck-turning members 22 parallelly to the associated swing pins 25,respectively; and urging means 26 comprising rubber bands 27, 28 forexerting swinging forces about proximal ends of the folding-back arms 21and directed toward a radial inside, onto the folding-back arms 21,respectively.

The folding-back rollers 23, 24 mounted on the neck-turning member 22 ofeach folding-back arm 21 are arranged in a mutually offset manner in alongitudinal direction, i.e., in a radial direction or axial directionof the building drum 1, and are provided to be protruded from theassociated neck-turning member 22 in a cooperative circumferentialdirection of the folding-back arms 21 such that protruded directions ofthe rollers 23, 24 are opposite to each other.

Further, the folding-back rollers 23, 24 are each divided into twoportions at both sides of those portions 22 a, 22 b of the neck-turningmember 22 which support the roller shafts for the rollers, respectively,i.e., the folding-back roller 23 is divided into a protruded roller 23 aand a non-protruded roller 23 b and the folding-back roller 24 isdivided into a protruded roller 24 a and a non-protruded roller 24 b. Atthis time, the roller rotational shaft supporting portion 22 a or 22 bcorresponding to one folding-back roller 24 or 23 has acircumferentially extended area positioned within a circumferentiallyextended area of the other folding-back roller 23 or 24.

The slide ring 30 of the thus adapted each folding-back means 8 has anaxially outer end to be urged by a driving mechanism (not shown), and isthus displaced toward an axial center. The rollers 23, 24 arestationarily placed on a sloped surface 71 a of each bead lock segment71 in a state where a tip end of the associated folding-back arm 21 isradially contracted. However, when the slide ring 30 is displaced towardthe axial center, the rollers 23, 24 are moved toward a radial outsidealong the sloped surface 71 a, and, in a state where a carcass bandcenter portion CBC is bulged, further moved toward the radial outsidebeyond the sloped surface 71 a and along a carcass band outer contour.

On this occasion, forces toward a radial inside are exerted on thefolding-back arms 21 by the associated urging means 26 comprising therubber bands 27, 28, and these forces are equally distributed to therollers 23, 24 by virtue of operations of the neck-turning member 22provided at tip ends of the folding-back arms 21, irrespectively of anouter contour of the carcass band center portion. Further, since therollers 23, 24 are mounted on the associated arm 21 at oppositecircumferential sides in an offset manner, the roller 23 of one arm 21protruded between neighboring folding-back arms 21 does not interferewith the roller 24 of another arm 21 even when tip end portions of thefolding-back arms 21 are radially contracted and thus the neighboringtip end portions are narrowed in spacing, thereby allowing spacingsbetween neighboring arms 21 to be minimized, and in this way, the arms21 can be densely arranged in the circumferential direction whileeliminating such a region of the carcass band side portion CBS which isnot pressure-jointed by any of the rollers 23, 24 in a state where thetip end portions of the arms 21 are radially expanded, thereby enablingstrong adhesion between the carcass band center portion CBC and thecarcass band side portion CBS and enabling prevention of a relativedisplacement therebetween.

Further, the rollers 23, 24 are each divided into two portions at bothsides of those portions 22 a, 22 b of the neck-turning member 22 whichsupport the roller shafts for the rollers, respectively, therebyenabling prevention of a problem that, if the rollers 23, 24 areprovided at only one sides of the portions 22 a, 22 b, respectively,there is a risk that: that portion of the carcass band side portion CBSwhich is stretched toward a radial outside between neighboringfolding-back arms 21 during folding back, is abutted on the non-rotatingsupporting portion 22 a and thus the carcass band side portion CBS isdamaged.

At this time, the roller rotational shaft supporting portion 22 a or 22b corresponding to one folding-back roller 24 or 23 has acircumferentially extended area positioned within a circumferentiallyextended area of the other folding-back roller 23 or 24, therebyenabling elimination of such a region of the carcass band side portionCBS which is not pressure-jointed by any of the rollers 23, 24.

It is noted that, in displacing each slide ring 30 to an axial outside,such a displacement can be conducted by operating the associated urgingmeans 26 by terminating the operation of the external driving mechanismfor driving the slide ring 30 toward an axial inside.

Further, since a folding back resistance is large at an initial stage offolding back and a folding back resistance is small at a final stage offolding back in folding back the carcass band side portion CBS by thefolding-back means 8, and since each slide ring 30 is urged by aconstant thrust force in the above configuration, the speed of the tipend of each arm 21, i.e., the rotational speeds of the associatedrollers are increased at those portions of the carcass band side portionCBS where the folding back resistance is small thereby shortening a timewhere the rollers stay on the carcass band side portion CBS per unitlength thereof, thereby possibly causing a problem that the carcass bandside portion CBS is not sufficiently pressure-jointed. As acountermeasure thereto, it is desirable to provide roller rotationalspeed restricting means for restricting the roller rotational speedcorrespondingly to this speed. FIG. 7 is a cross-sectional view showingan example of a folding-back roller provided with the roller rotationalspeed restricting means which can be adapted such that the folding-backroller 23 a is adapted with an outer rolling wheel 61, an inner fixingmember 62, and viscous resistive fluid such as silicone oil 63 filledwithin a hermetically sealed space between them, and this roller 23 a isfixed to the roller shaft 22 b of the neck-turning member 22 by fittinga key to a key groove (both not shown), and in this case, rotationalspeeds of the roller are restricted by virtue of the viscosity of theviscous resistive fluid when the rotational speeds are increased,thereby enabling the rotational speed of the roller to be uniformalized.

FIGS. 8 through 11 are cross-sectional views of a tire in course ofmolding, illustrating a tire building process using the above describedtire building drum 1. In molding a tire by the building drum 1:

as shown in FIG. 8 a, arranged on an outer peripheral side of the tirebuilding drum 1 are: preset beads PB each provided by presetting a beadcore B and a bead filler material F; and a carcass band CB provided byassembling members such as an inner liner member IL, canvas chafermember CF, onto a carcass member C to thereby exhibit a cylindricalshape as a whole;

as shown in FIG. 8 b, then the bead lock segments 71 of the bead lockmeans 7 are radially expanded to lock the bead cores B, respectively, byadvancingly displacing the bead lock pistons 37 shown in FIG. 1 underoperation of the links 72; and

as shown in FIG. 8 c, a space hermetically sealed by the center bladder9 is pressurized so that the center portion CBC of the carcass band CBextending between the bead cores B is bulged into a toroidal shape,while displacing the bead cores B close to each other under operation ofthe sliders 4 shown in FIG. 1, with the bead cores B locked to thecorresponding bead lock segments 71, respectively.

Next, as shown in FIG. 9 a, the rigid support members 10 a are displacedto be radially expanded to a height where the side surfaces of the rigidsupport members 10 a correspond to radial positions of the bead cores B,respectively, and the rigid support members are held at these positions,respectively. In this state, there are provided clearances between aninner surface of the center bladder 9 and the side surfaces of the rigidsupport members 10 a, for allowing the rigid support members 10 a to beradially expanded without interference with the center bladder 9. Then,as shown in FIG. 9 b, the bead lock segments 71 at both sides aredisplaced close to each other under operation of the sliders 4, therebydisplacing the inner surface of the center bladder 9 to the sidesurfaces of the rigid support members 10 a as close as possible, tobring the clearances therebetween to be substantially zero. Further, asshown in FIG. 9 c, the folding-back means 8 are operated to therebydisplace the proximal ends of the folding-back arms 21 toward the axialcenter, thereby starting to fold back the carcass band side portionsCBS. It is noted that the steps shown in FIG. 9 a and FIG. 9 b areconducted for the purpose of tightly folding back the carcass band CBaround the bead cores B to achieve an excellent bead firmness then.

Subsequently, as shown in FIG. 10 a, the folding-back rollers 23, 24 aredisplaced to a radial outside along an outer contour of the carcass bandcenter portion CBC, thereby finishing folding back of the carcass bandside portions CBS. In conducting such folding back, the folding-backarms 21 are provided with the associated folding-back rollers 23, 24 inthe offset manner in both the circumferential direction and radialdirection as described above, respectively, so that the folding-backarms 21 can be arranged close to each other without mutual interferenceof the folding-back rollers 23, 24 mounted on the mutually neighboredfolding-back arms 21, respectively, while eliminating such a regionwhich is not pressure-jointed by any of the rollers 23, 24 even in astate where the folding-back arms 21 are radially expanded, therebystrengthening the pressure-joint at the folded back portions.

It is noted that the rigid support members 10 a are desirably to bedisplaced to be radially expanded synchronizedly with the radialexpansion of the folding-back rollers 23, 24 in order that the sidesurfaces are constantly opposed to the folding-back rollers 23, 24 asthey are radially expanded, correspondingly to the radial positions ofthe thus radially expanded folding-back rollers 23, 24 in folding backthe carcass band side portions CBS by the folding-back rollers 23, 24,respectively, thereby further ensuring the pressure-jointing of thecarcass band side portions CBS onto the carcass band center portion CBC.

As shown in FIG. 10 b after the folding-back rollers 23, 24 have beendisplaced to the radial inside as they were, portions of the carcassband side portions CBS near folded back ends thereof arepressure-jointed by stitching rollers 38 each having a surface subjectedto a knurling treatment, while rotating the tire building drum 1.Subsequently, as shown in FIG. 10 c, the rigid support members 10 a areradially expanded more, and at this time, this radial expansion isconducted while reducing an internal pressure of the center bladder 9 todecrease a tension of the center bladder 9, thereby enabling the rigidsupport members 10 a to be radially expanded smoothly. Meanwhile,tensions of carcass cords extending between the paired bead lock means 7also act as factors which obstruct a smooth radial expansion of therigid support members 10 a, i.e., of the core body 10. Althoughresistances increased in this way against the radial expansion of thecore body 10 lead to increased loads of a motor for driving the sleevereciprocative driving means for displacing the sleeves carrying thereonthe core body 10 toward and away from each other, the radial expansionof the core body can be made smooth, by setting a process for varying aninternal pressure of the center bladder 9 or varying a spacing betweenthe pair of bead locks correspondingly to an outer diameter of the corebody, or by controlling at least one of the internal pressure of thecenter bladder 9 and the spacing between the pair of bead locks based ona load value of the motor in a real-time manner, while utilizing thefact of the increased load and in a manner that the load value does notexceed a predetermined magnitude.

Thereafter, as shown in FIG. 11 a, two or more layers of belt members1B, 2B are assembled in this order onto an outer periphery of thecarcass band center portion CBC along the outer peripheral surfaces ofthe rigid support members 10 a, then belt reinforcing members (notshown) such as spiral layers are assembled as required, and then a treadrubber T is assembled onto an outer periphery thereof. Next, as shown inFIG. 11 b, sidewall rubbers SW and rubber chafer members GC areassembled onto side surfaces of the carcass band CB having the foldedback side portions, respectively, to thereby complete a green tire, andthereafter, as shown in FIG. 11 c, an outer periphery of the green tireis gripped by an outside grip ring 39 to detach the green tire from thetire building drum 1.

It is possible here to arrange such a rubber at a portion of thesidewall rubbers SW, which is white in color different from that of thesurrounding.

There will be explained a second embodiment according to the presentinvention based on FIG. 12. While FIG. 12 is a cross-sectional viewschematically showing substantially half of a tire building drum 1A ofthis embodiment, the tire building drum 1A of this embodiment is amodification of the tire building drum 1 of the first embodiment and isdifferent therefrom only in that structures of the sleeve 3 and slider 4are partially different from those in the first embodiment and theconfiguration for reciprocally driving them is different, while the corebody 10 mounted on the sleeves 3, and the bead lock means 7,folding-back means 8 and center bladder 9 mounted on the sliders 4 arefully the same as those in the first embodiment, so that referencenumerals in FIG. 12 corresponding to them are made the same and detaileddescription thereof is omitted for simplicity. Further, the tirebuilding method for molding a tire by utilizing these means are also thesame as those in the first embodiment, so that explanation of the formeris also omitted.

It is noted that FIG. 12 a shows a state where the core body 10 isradially expanded and the bead lock means 7 are displaced close to eachother, and FIG. 12 b shows a state where the core body 10 is radiallycontracted and the bead lock means 7 are displaced away from each other.

Firstly, in radially expanding a pair of core bodies 10, sleeves 3A aredisplaced close to each other by reciprocative driving means for thesleeves 3A to displace end portions of a pair of links 11 a coupled tothe sleeves 3A close to each other, respectively, and the sleevereciprocative driving means for displacing the sleeves 3A are adaptedwith: female screw members 41A coupled to the sleeves 3A at radialinsides thereof through coupling members 42A, respectively; a screwshaft 50A disposed in a hollow of the center shaft 2 and having rightand left male screw portions 51A threadedly engaged with the associatedfemale screw members 41A, respectively; and screw shaft rotating means(not shown) for rotating the screw shaft 50A; in which the right andleft male screw portions 51A of the screw shaft 50A have mutuallyopposite lead orientations, respectively. Based on this configuration,the screw shaft 50A is rotated by the screw shaft rotating means todisplace the female screw members 41A toward and away from each other ina left-right symmetric manner, thereby allowing the pair of core bodies10 installed on the sleeves 3A to be precisely expanded or contracted.It is noted that the center shaft 2 is formed with an elongatedthrough-hole 2 b for allowing the coupling members 42A to penetratetherethrough.

Next, bead lock reciprocative driving means for displacing the pairedbead lock means 7 close to each other may be adapted with: screwportions 12A formed at end portions of sliders 4A having the bead lockmeans 7 mounted thereon, respectively, so as to have mutually oppositescrew thread extending directions for the right and left sliders 4A,respectively; associated screw blocks 13A threadedly engaged with thescrew portions, respectively; and rotating means (not shown) forrotating the sliders 4A and the screw blocks 13A relative to each other.Further, provided at end portions of the center shaft 2 are stoppers 14Afor restricting axial displacements of the screw portions 12A of sliders4A, respectively.

Although the screw portions 12A and screw blocks 13A in FIG. 12 areadapted with male screws and female screws, respectively, reversecombinations are possible.

Here, the means for rotating the screw portions 12A and screw blocks 13Arelative to each other, and means for restricting rotations of the screwportions 12A relative to the center shaft 2 so as to keep axialpositions of the paired sliders 4A constant to thereby fix the axialpositions of the bead lock means, have been explained in the firstembodiment, so that detailed description thereof is omitted.

There will be explained a third embodiment according to the presentinvention based on FIGS. 13 through 21. FIG. 13 is a cross-sectionalview of a tire building drum 100 of this embodiment.

This tire building drum 100 comprises: a hollow center shaft 110; a pairof bead lock means 120 for locking both bead cores; a pair of corebodies 130 for supporting a carcass band from a radial inside, andadapted to be axially displaced toward and away from each other andadapted to be deformed and thereby expanded or contracted; core-bodyexpanding/contracting means 160 for expanding or contracting the corebodies 130; and a pair of folding-back means 170 for folding backcarcass band side portions around associated bead cores, respectively;in which the drum is provided with a pair of sliders 140 to be displacedtoward and away from each other on the center shaft 110, and each slider140 has mounted thereon the bead lock means 120, core body 130 andfolding-back means 170 positioned at the axially same side as the slider140.

Disposed in a hollow of the center shaft 110 is a screw shaft 150constituting a part of slider reciprocative driving means for displacingthe pair of sliders 140, and the core bodies 130 each comprise aplurality of rigid support members 131 toroidally arranged and displacedand thereby expanded or contracted.

There will be now explained interconnection between the tire buildingdrum 100 and a tire building machine 102 for supporting and driving it,with reference to a diagrammatic arrangement view of the tire buildingmachine shown in FIG. 18. The tire building machine 102 comprises: amolding machine body part 103A having the center shaft 110 of the tirebuilding drum 100 mounted thereon, and for rotationally driving thecenter shaft 110; and an opposite driving end supporting part 103B forsupporting an end of the center shaft 110 opposite to its driving end.The tire building machine 102 further comprises: a slider driving part104 comprising an external shaft 104B coupled to the screw shaft 150 ofthe tire building drum 100, and a rotation servomotor 104A for rotatingthe screw shaft 150 through the external shaft 104B; and a reciprocativedriving part 105 comprising a right/left screw 105B, and a pair ofdriving arms 105C threadedly engaged with the right/left screw 105B soas to be moved equidistantly in a right-and-left direction. The drivingarms 105C of this reciprocative driving part 105 are constitutionallyadapted to be displaced close to and away from an axis of the tirebuilding drum 100, and these driving arms are each provided with, at tipends thereof: a clamper 106 to be engaged with an external drivecoupling part 165 of the core-body expanding/contracting means 160; andfolding-back pawls 107 to be abutted on the associated folding-backmechanism 170 to thereby operate the same.

There will be explained respective main parts constituting the tirebuilding drum 100. As shown in FIG. 13, each slider 140 is adapted with:a slider guide part 142 to be axially slid on the center shaft 110; anda bead lock means supporting part 143 fixedly mounted on the sliderguide part 142 and extending to a radial outside from the slider guidepart 142.

The slider reciprocative driving means for displacing the sliders 140are adapted with: female screw members 154 coupled to the slider guideparts 142 of the sliders 140 at radial insides of the slider guideparts, respectively; the screw shaft 150 threadedly engaged with thefemale screw members; and screw shaft rotating means (not shown) forrotating the screw shaft; and the screw shaft 150 is provided with apair of right and left male screw portions 151 having mutually oppositeleads, and a slider drive coupling portion 152 for coupling the screwshaft 150 to the external shaft 104B.

Based on this configuration, the screw shaft 150 is rotated from theexterior through the slider drive coupling portion 152, to thereby movethe female screw members 154 threadedly engaged with the male screwportions 151 by equal distances in axially opposite directions,respectively, thereby allowing the respective sliders 140 to bedisplaced toward and away from each other.

The respective sliders 140 are precisely moved in axially mutuallyopposite directions by equal distances, respectively, by rotation of thescrew shaft 150 as described above, thereby enabling precise achievementof so-called widthwise approach where the bead lock means 120 and corebodies 130 are caused to approach an axial center synchronizedly withradial expansion of the core bodies 130 in bulging a carcass band centerportion while maintaining path lengths of cords extending between beadcores. Further, the sliders 140 are driven by the exterior servomotor104A through the screw shaft 150 such that the sliders can be stopped atarbitrary axial positions, so that such tires having different lengthsof carcass cords extending between bead cores, and/or having differentwidths of belt members, can be continuously molded without exchangingthe above described members of the drum 100.

Provided between the right and left sliders 140 is an center bladder 145deformable for expansion or contraction to hermetically seal a spacedelimited by the sliders 140, and the center bladder 145 has both axialside portions mounted to axially center-side ends of the bead lock meanssupporting parts 143 of the sliders 140, respectively. This centerbladder 145 is adapted to cover, in a tensioned state, those gapsbetween rigid support members 131 constituting the core bodies 130 at anouter peripheral surface to be formed when the members 131 are radiallyexpanded, thereby allowing a carcass member body portion to be moreuniformly supported, and thereby allowing configuration of a uniformbonding surface upon bonding a belt member onto the center bladder 145,thereby enabling contribution to improved uniformity.

FIG. 14 through FIG. 17 are partially cut-away detailed partial views ofthe sliders 140, core-body radially expanding means 160, bead lock means120, and folding-back means 170 in different states of the tire buildingdrum, respectively, and the respective members will be explained indetail based on these figures. Here, although only FIG. 14 shows a statewhere the sliders 140 are located at axially outer positions,respectively, all FIG. 15 through FIG. 17 show states where the sliders140 have been displaced to an axial center side, respectively.

As shown in FIG. 14, the right and left core-body radially expandingmeans 160 for displacing the rigid support members 131 to expand orcontract them, each comprise: expanding/contracting link parts 161annularly arranged to be coupled to the associated rigid support members131 to thereby expand or contract them, respectively; a link unitingpart 162 for uniting these expanding/contracting link parts 161 andaxially slid on the associated slider guide part 142; a longitudinalmovement screw member 164 coupled to the link uniting part 162 through acoupling rod 163, and adapted to be axially displaceable while rotationof the longitudinal movement screw member 164 around the center shaft110 being restrained; a screw block 165 threadedly engaged with thelongitudinal movement screw member 164 through trapezoidal threads, andadapted to be axially fixed and circumferentially rotatable; and a brake166 functioning as relative rotation restricting means for restricting arotation of the screw block 165 relative to the center shaft.

Each expanding/contracting link part 161 is adapted with: a pair ofparallel links 161A each having opposite ends hinged to a pin mounted onthe associated link uniting part 162 and to a pin coupled to theassociated rigid support member 131, respectively, so that the parallellinks are swung parallelizedly; and a swing link 161B having oppositeends hinged to a pin mounted on one of the parallel links 161A and to apin fixedly provided at the link uniting part 162.

Each screw block 165 is born by a support ring 167 fixed concentricallywith the center shaft 110. When the center shaft 110 is rotated afterthe brake 166 is released in a state shown in FIG. 15 and each drivingarm 105C of the tire building machine 102 is brought close to a tirebuilding drum axis such that the screw block 165 is clamped and fixed bythe clamper 106 provided at the tip end of the associated driving arms105C, the longitudinal movement screw member 164, coupling rod 163, andlink uniting part 162 are integrally moved to an axial inside into astate shown in FIG. 16 because the longitudinal movement screw member164 is coupled to the associated coupling rod 163 the rotation of whichrelative to the center shaft 110 is restrained by the associated sliderguide part 142. In actually bulging a carcass band center portion, therigid support members 131 are radially expanded while being moved to anaxial center, so that each link uniting part 162 is moved to an axialcenter side by a displacement larger than a displacement of theassociated slider guide part 142 of the associated slider 140 to bemoved to the axial center. Namely, each link uniting part 162 is movedto the axial center relative to the associated slider guide part 142, sothat the swing link 161B and the pair of parallel links 161A both hingedto the associated link uniting part 162 cooperate with each other,thereby allowing the rigid support members 131 to be radially expandedwhile maintaining postures thereof, respectively.

There will be now additionally explained the brakes 166 functioning asthe means for restricting rotations of the screw blocks 165 relative tothe center shaft 110. Each screw block 165 has a female screw portion165A threadedly engaged with a male screw portion 164A of the associatedlongitudinal movement screw member 164 through trapezoidal threads,thereby allowing, by virtue of an effect of this threaded engagement,counteraction against a contracting force of the center bladder 145 andagainst a force radially contracting segments upon bonding a belt memberwith tension onto an outer periphery of the center bladder 145.Nonetheless, to avoid dislocation of each screw block 165 due tovibration, impact or the like, the brake 166 is mounted on theassociated support ring 167 and a brake disk (not shown) is protruded toabut on a brake working face 165B of the screw block 165, therebyenabling the screw block 165 to be assuredly fixed relative to thecenter shaft 110.

In radially contracting the rigid support members 131, there isconducted an operation reverse to the radial expansion, i.e., the centershaft 110 of the tire building drum is rotated reversely to that ofradial expansion of the rigid support members 131 while clamping eachscrew block 165 by the associated clamper 106, so that the associatedlongitudinal movement screw member 164, coupling rod 163 and linkuniting part 162 are integrally moved to the axial outside, therebyallowing the rigid support members 131 to be radially contracted.Further, each support ring 167 is provided with an axial inside surface167A to be abutted on an axial outer end surface 164B of the associatedlongitudinal movement screw member 164, and these surfaces are abuttedon each other so that radial positions of the rigid support members 131are kept constant when the rigid support members 131 are radiallycontracted to the minimum. In starting the radial contraction of theradial contracting operation, it is important to weaken a radiallycontracting force of the center bladder 145 by increasing an internalpressure of the center bladder 145, so as to release a self-locked stateof the longitudinal movement screw member 164 and the associated screwblock 165 which are tightly and threadedly engaged with each otherthrough the trapezoidal threads. Further, to cause the axial outer endsurface 164B of the longitudinal movement screw member 164 to be abuttedon the axial inside surface 167A of the associated support ring 167without impact, it is also important that the clamping force of theassociated clamper 106 is lowered just before this abutment, so that theclamper 106 and screw block 165 are slid with each other when the axialinside surface 167A abuts on the associated longitudinal movement screwmember 164.

There will be now explained the bead lock means 120. Although it is alsopossible in this embodiment to employ the same one as the bead lockmeans 7 in the building drums 1, 1A in the above described first andsecond embodiments, there will be described in this embodiment anotherexample having a configuration slightly different from the above. Eachbead lock means 120 comprises: bead lock segments 121 which arecircumferentially arranged adjacent to each other so to be expanded orcontracted in an annular shape; bead lock expanding/contracting linkparts 122 coupled to the associated bead lock segments 121,respectively; bead lock pistons 125 coupled to these link parts 22,respectively, and axially movable; bead lock cylinders 124 for axiallymoving these bead lock pistons 125, respectively; and a bead lockcylinder driving ring 126 engaged with the associated bead lockcylinders 124 and threadedly engaged with the associated bead lock meanssupporting part 143 of the slider 140.

Each bead lock expanding/contracting link part 122 is adapted with: apair of parallel links 122A each having opposite ends hinged to theassociated bead lock segment 121 and associated bead lock piston 125,respectively; and a swing link 122B having opposite ends hinged to theassociated bead lock segment 121 and associated bead lock cylinder 124,respectively.

As the bead lock cylinders 24 are pressurized at interior thereof in astate shown in FIG. 14 to thereby move the bead lock pistons 125 to theaxial center, the bead lock segments 121 can be radially expanded asshown in FIG. 15 while maintaining postures thereof by virtue offunctions of the parallel-links 122A and swing links 122B. Further, asthe bead lock cylinders 124 are brought to negative pressures at theinterior thereof, the bead lock pistons 125 are moved to an axialoutside, thereby enabling the bead lock segments 121 to be radiallycontracted through the bead lock expanding/contracting link parts 22.

As each bead lock cylinder driving ring 126 threadedly engaged with theassociated bead lock means supporting parts 143 is rotated around thecenter shaft from the state shown in FIG. 14, the bead lock cylinderdriving ring 126 is displaced to the axial outside while being rotatedand the associated bead lock cylinders 124 provided with engagement pins124A to be engaged with the bead lock cylinder driving ring 126 are alsodisplaced to the axial outside without rotation because the associatedbead lock pistons 125 are restrained in rotation around the center shaftby rotation lock keys 125A, respectively. As a result, the associatedbead lock segments 121 can also be displaced to the axial outside tothereby ensure a clearance at the axial outside of the center bladder145 for detaching an associated bladder ring 145A for latching anassociated edge portion of the center bladder 145, thereby resultinglyfacilitating an exchanging operation of the center bladder 145. Thesescrew portions provided at the bead lock means supporting parts 143, thebead lock cylinder driving rings 126 threadedly engaged therewith, andthe rotation lock keys 125A cooperatively establish means for varying anaxial position of that bead lock means 120 relative to an axial sideportion of the center bladder 145, which is located at the same axialside as this axial side portion.

There will be now explained the pair of right and left folding-backmechanisms 170. Although it is also desirable in this embodiment toutilize the same one as the folding-back means 8 in the building drums1, 1A in the above described first and second embodiments, there will bedescribed in this embodiment another example having a configurationslightly different from the above.

The right and left folding-back means 170 each comprises: a base part171 fixedly coupled to the bead lock means supporting part 143 of theassociated slider 140; folding-back rollers 172 which arecircumferentially arranged adjacent to each other so to be expanded orcontracted in an annular shape; a roller exterior drive abutment part173 to be abutted on the associated folding-back pawls 107 which areprovided at the tip end of the driving arm 105C of the tire buildingmachine 102 and which is reciprocally displaced axially, so that theroller exterior drive abutment part 173 is slid and reciprocallydisplaced on the associated base part 171; folding-back arms 174 eachhaving one end coupled to the associated folding-back roller 172 and theother end hinged to the associated roller exterior drive abutment part173; a return spring 175 having opposite ends secured to the associatedbase part 171 and roller exterior drive abutment part 173, respectively;and a plurality of rubber bands 176 fixedly provided around outerperipheries of the associated folding-back arms 74. It is noted that thefolding-back pawls 107 are provided by at least two in number at asymmetric arrangement with respect to a drum rotational axis, so as toapply forces parallel to the axis to the associated roller exteriordrive abutment part 173 to thereby axially move the same.

In FIG. 16, provided on an outer peripheral surface formed by annularlyarranged folding-back arms 174 is an associated fold-back portion Xcomprising a side portion of a carcass band or comprising a sidewallrubber in addition thereto, and this fold-back portion X is folded backby radially expanding the folding-back arms 174 and the associatedfolding-back rollers 172 coupled thereto, respectively. Namely, wheneach driving arm 105C is brought close to the axis of the tire buildingdrum 100 and the driving arm 105C is moved to the axial center tothereby cause the associated folding-back pawls 107 to abut on theassociated roller exterior drive abutment part 173 to thereby furthermove it to the axial center side, the roller exterior drive abutmentpart 173 is moved to the axial center along the associated base part 171as shown in FIG. 17 so that the associated folding-back arms 174 hingedto the roller exterior drive abutment part 173 as well as thefolding-back rollers 172 are also moved to the axial center. However,the folding-back rollers 172 are restricted in movement to the axialcenter side by the radially expanded center bladder 145, with thefold-back portion X interposed therebetween. Thus, the folding-back arms174 and folding-back rollers 172 are radially expanded around hingedpoints between them and the roller exterior drive abutment part 173,thereby allowing the fold-back portion X to be folded back.

To radially contract the folding-back rollers 172 and folding-back arms174 after radially expanding them and folding back the associatedfold-back portion X, the associated roller exterior drive abutment part173 is moved to the axial outside by a function of the associated returnspring 175, and the folding-back arms 174 are radially contracted byfunctions of the associated rubber bands 176.

There will be now explained an example of procedure for molding a greentire by using the tire building drum 100 based on partially cut-awayfront views shown in FIG. 19 through FIG. 21, respectively. As shown inFIG. 19, in a state of this tire building drum 100 where the rigidsupport members 131, bead lock segments 121, and folding-back arms 174are radially contracted, arranged at a radial outside of this drum 1 isa carcass band CB having previously assembled thereon preset beads PBmolded by another drum. At this time, the spacing between the bead locksegments 121 of both the bead lock means 120 is set correspondingly to aspacing between both bead cores B of the carcass band CB which has beenset correspondingly to each tire size.

Subsequently, as shown in FIG. 20, the bead lock segments 121 areradially expanded to retain the preset beads PB, and thereafter therigid support members 131 and the center bladder 145 are radiallyexpanded while narrowing an axial spacing between the bead lock means120. At this time, there is adjusted an internal pressure of the centerbladder 145 correspondingly to a diameter of the center bladder 145, soas to prevent an unnecessary radially contracting force from acting onthe rigid support members 131 and so as to cause a uniform tension toact on the center bladder 145.

Next, as shown in FIG. 21, the rigid support members 131 and the centerbladder 145 are radially expanded to predetermined maximum diameters,respectively, correspondingly to a tire size, and thereafter thefolding-back arms 174 are radially expanded while moving them toward theaxial center side, thereby folding back the fold-back portions X. Then,bonded onto an outer periphery of the radially expanded carcass band CBare a belt member and a tread rubber, thereafter ribbon-like sidewallrubbers are wrapped onto tire side portions to thereby form sidewallrubbers having predetermined cross-sectional shapes, respectively, andthen stitching operations are applied to the sidewall rubbers, therebycompleting a green tire. Thereafter, the folding-back arms 174, centerbladder 145, rigid support members 131, and bead lock segments 121 areradially contracted, and the green tire is taken out.

Here, in case that sidewall rubbers interfere with the bead locksegments 121 upon wrapping the sidewall rubbers while keeping bead lockin forming the sidewall rubbers, it is even possible to radiallycontract the bead lock segments 121 in advance of wrapping of thesidewall rubbers at the interfering portion, and to increase an internalpressure of the center bladder 145 to thereby retain the green tire incourse of molding from inside thereof without bead lock.

While the first through third embodiments have been described, the screwshafts 50, 50A, 150 have been provided in the hollow of the centershafts 2, 110, respectively, in any of the embodiments. Althoughrotational angles of these screw shafts from origins are varied in aone-to-one corresponding manner with respect to screw shaft rotationangle information held in a molding machine side while the building drumis mounted on the molding machine, the screw shafts are very likely tobe rotated by external forces such as due to vibration, impact or thelike which act during handling when the building drums 1, 1A, 100 arebrought into states detached from the molding machine for exchange orrepair. Thus, at the time of mounting each screw shaft to the moldingmachine again, it is required that the screw shaft is restored into itsoriginal state or the screw shaft rotation angle information held at themolding machine side is required to be set again correspondingly to arotation angle at the time when the screw shaft is mounted again,thereby requiring a so-called originating operation. This operationrequires extensive time and steps, and to deal with this problem, thereis provided screw shaft origin posture holding means.

This screw shaft origin posture holding means will be explained bytaking the third embodiment for example, with reference to FIG. 22showing a partial cross-section of the center shaft 110. Formed througha center shaft flange 111 of the center shaft 110 acting as a fasteningportion to a molding machine side, is a through-hole 111B in radialdirection, and a lock pin 112 is fitted through this through-hole 111B.Provided in the through-hole 111B and radially outside the lock pin 112,is urging means 116 for urging the lock pin 112 to a radial inside, andan end of this urging means 116 opposite to the lock pin 112 is fixed tothe center shaft flange 111. The lock pin 112 has a radial inside endformed into a conical projection 112A which is adapted to be engagedwith a concave 155 formed on a peripheral surface of the screw shaft 150in a state where the lock pin 112 is displaced to the radial inside tothereby restrict rotation of the screw shaft 150.

Further, formed on the peripheral surface of the lock pin 112 at a drummounting flange surface 111A side, is a cavity 113, and this cavity 113has arranged therein a plurality of needle bearings 117 each oriented ina circumferential direction such that a plane circumscribed by theseneedle bearings 117 defines a tapered surface 113A tapered with respectto a radial direction.

Furthermore, there is formed an axial hole 111C penetrating between thethrough-hole 111B of the center shaft flange 111 and the drum mountingflange surface 111A; provided in the axial hole 111C is a wedge member114 to be displaced along this axial hole; mounted on an end at the drummounting flange surface 111A side of the wedge member 114, is a pin 115;and an end surface of the through-hole 111B side defines an inclinedsurface 114A to be engaged with the tapered surface 113A. Then, the lockpin 112, the concave 155 of screw shaft 150, the urging means 116, andthe wedge member 114 cooperatively establish the screw shaft originposture holding means.

In a state where the tire building drum 100 having such screw shaftorigin posture holding means is mounted on a molding machine, the pin115 is pushed by a flange at the molding machine side so that the wedgemember 114 is pushed into the through-hole 111B side, and this pushingforce acts to displace the lock pin 112 to the radial outside throughthe needle bearings 117 arranged in the tapered surface 113A and engagedwith the inclined surface 114A of the wedge member 114, therebyresultingly allowing the screw shaft 150 to be rotated without beinglocked by the lock pin 112.

Here, zero return is to be conducted by returning a rotation angle ofthe screw shaft 150 to its origin when the drum 100 is detached from themolding machine, and at this time, there is settled a position of theorigin such that the concave 155 of the screw shaft 150 is directedtoward the projection 112A of the lock pin 112. When the building drum100 in this state is detached from the molding machine, there isreleased the force which has acted through the pin 115 and wedge member114 and which is in a direction for displacing the lock pin 112 to theradial outside, so that the projection 112A of the lock pin 112 isallowed to be engaged with the concave 155 of the screw shaft 150 byvirtue of function of the urging means 116, and in this way, the screwshaft 150 can be fixedly held so as not to rotate relative to the centershaft 110 even in a state where the building drum 100 is detached from amolding machine. By virtue of this screw shaft origin posture holdingmeans, it is possible to automatically restrain and release rotation ofthe screw shaft 150 by simply attaching and detaching the building drum100 to and from a molding machine, thereby enabling the drum 100 to beautomatically exchanged.

INDUSTRIAL APPLICABILITY

It will be appreciated form the foregoing description that, according tothe present invention, upon assembling tire component members such as abelt member, tread rubber, sidewall rubbers and the like onto an outsideof a bulged carcass band center portion, these component members aredirectly assembled on a building drum having previously arranged thereonthe carcass band, and at this time, a toroidal core body is radiallyexpanded to a maximum diameter while locking bead cores acting to latchopposite ends of the carcass band center portion and the tire componentmembers are assembled based on the toroidal core body, thereby enablingprecise assembling of the tire component members, with high precision inpositions of the tire component members relative to both bead cores.

1. A tire building drum comprising: a pair of bead lock means adapted tobe displaced toward and away from each other and thereby expanded orcontracted; carcass band folding-back means, positioned adjacent to thebead lock means, respectively; and a center shaft for supporting thesemeans; wherein said tire building drum further comprises at least onecore body at an axial inside of said bead lock means, said core bodycomprising a plurality of sheets of rigid support members toroidallydisposed and adapted to be displaced and thereby expanded or contracted.2. The tire building drum of claim 1, further comprising: a centerbladder deformable for expansion or contraction, which extends at aradial outside of said core body, and which has both axial side portionsadapted to be displaced toward and away from each other integrally withsaid bead lock means, respectively; wherein said rigid support membersare provided with comb tooth portions, respectively, for engagement ofsaid rigid support members with each other.
 3. The tire building drumaccording to claim 1, wherein said bead lock means each comprise: beadlock segments circumferentially arranged adjacent to each other so as tobe expanded or contracted in an annular shape; associated links havingone ends hinged to said bead lock segments, respectively; bead lockpistons coupled to other ends of said links, respectively, and providedin an axially displaceable manner; and bead lock cylinders adapted todisplace the associated bead lock pistons, respectively.
 4. The tirebuilding drum according to claim 3, further comprising: means forvarying an axial position of that bead lock means relative to an axialside portion of said center bladder, which is located at the same axialside as the axial side portion of the center bladder.
 5. The tirebuilding drum according to claim 1, wherein said carcass bandfolding-back means are adapted to be displaced toward and away from eachother, integrally with said bead lock means at the axially same sides assaid carcass band folding-back means, respectively; and wherein each ofsaid carcass band folding-back means includes: a plurality offolding-back arms arranged in a circumferential direction and having tipend portions at axial insides, respectively; neck-turning members hingedto the tip end portions of said folding-back arms, respectively, so asto be swung to radial inside and outside; folding-back rollerscircumferentially extending and born by longitudinal opposite endportions of the associated neck-turning members, respectively; a slidering hinged to proximal ends of said plurality of folding-back arms andadapted to be displaceable to axial inside and outside relative to theassociated bead lock means; and urging means for exerting a swingingforce directed toward a radial inside, onto said folding-back arms. 6.The tire building drum according to claim 5, wherein each of a pair ofsaid folding-back rollers born by the associated neck-turning member isdivided into two portions at both sides of an associated portion of saidneck-turning member for supporting the folding-back roller, and iscircumferentially protruded from the associated neck-turning member, sothat protruded directions of said pair of folding-back rollers areopposite to each other, and so that a roller rotational shaft supportingportion corresponding to one of said pair of folding-back rollers has acircumferentially extended area positioned within a circumferentiallyextended area of the other folding-back roller.
 7. The tire buildingdrum according to claim 5, wherein each of said folding-back rollers isprovided with roller rotational speed restricting means for restrictinga roller rotational speed correspondingly to this speed.
 8. The tirebuilding drum according to claim 1, wherein said core body is providedby one in number and arranged in-between said pair of bead lock means;and wherein said tire building drum further comprises: a pair of sleevesadapted to be displaced toward and away from each other on said centershaft; sleeve reciprocative driving means for displacing said sleeves;and link mechanisms having one ends coupled to said rigid supportmembers, respectively, and the other ends coupled to said pair ofsleeves, respectively, said link mechanisms being each adapted with apair of links having intermediate portions hinged to each other,respectively.
 9. The tire building drum according to claim 8, whereinsaid sleeve reciprocative driving means is adapted with: screw portionsformed at end portions of said sleeves, respectively, and havingmutually opposite lead orientations for the right and left sleeves,respectively; screw blocks threadedly engaged with said screw portions,respectively; and rotating means for relatively rotating said sleevesand the associated screw blocks, respectively; wherein said tirebuilding drum further comprises: sliders having mounted thereon saidbead lock means, respectively, and adapted to displace said bead lockmeans toward and away from each other; and bead lock reciprocativedriving means for displacing said pair of bead lock means; and whereinsaid bead lock reciprocative driving means is adapted with: female screwmembers coupled to radial insides of said sliders, respectively; a screwshaft disposed in a hollow of said center shaft and having right andleft male screw portions threadedly engaged with the associated femalescrew members, respectively; and screw shaft rotating means for rotatingthe screw shaft; in which said right and left male screw portions ofsaid screw shaft have mutually opposite lead orientations, respectively.10. The tire building drum according to claim 8, further comprising:means for restraining rotation of said screw blocks; and means forrotating, together with said sleeves, said center shaft fitted throughsaid sleeves by circumferential convex and concave.
 11. The tirebuilding drum according to claim 9, further comprising: means forrotating both said screw blocks synchronizedly with each other; andmeans for fitting said sleeves onto said center shaft by circumferentialconvex and concave.
 12. The tire building drum according to claim 10,further comprising: means for restricting rotation of said screw blocksrelative to said center shaft.
 13. The tire building drum according toclaim 8, wherein said sleeve reciprocative driving means is adaptedwith: female screw members coupled to said sleeves at radial insidesthereof, respectively; a screw shaft disposed in a hollow of said centershaft and having right and left male screw portions threadedly engagedwith the associated female screw members, respectively; and screw shaftrotating means for rotating the screw shaft; in which the right and leftmale screw portions of said screw shaft have mutually opposite leadorientations, respectively; wherein said tire building drum furthercomprises: sliders having mounted thereon said bead lock means,respectively, and adapted to displace said bead lock means toward andaway from each other; and bead lock reciprocative driving means fordisplacing said pair of bead lock means; and wherein said bead lockreciprocative driving means is adapted with: screw portions formed atend portions of said sliders, respectively, so as to have mutuallyopposite screw thread extending directions for the right and leftsliders, respectively; screw blocks threadedly engaged with said screwportions, respectively; and rotating means for rotating said sliders andsaid screw blocks relative to each other.
 14. The tire building drumaccording to claim 13, further comprising: means for restrainingrotation of said screw blocks; and means for rotating, together withsaid sliders, said center shaft fitted through said sliders bycircumferential convex and concave.
 15. The tire building drum accordingto claim 13, further comprising: means for rotating both said screwblocks synchronizedly with each other; and means for fitting saidsliders onto said center shaft by circumferential convex and concave.16. The tire building drum according to claim 14, further comprising:means for restricting rotation of said screw blocks relative to saidcenter shaft.
 17. The tire building drum according to claim 1, whereinsaid core bodies are provided by two in number, and said core bodies arearranged near axial insides of said pair of bead lock means,respectively; wherein said tire building drum further comprises: a pairof sliders having mounted thereon said core bodies and said bead lockmeans located at the axially same sides as said sliders, respectively;slider reciprocative driving means for displacing said sliders,respectively; and core-body expanding/contracting means for expanding orcontracting said core bodies, respectively; and wherein each of saidcore-body expanding/contracting means is adapted with:expanding/contracting link parts coupled to said rigid support membersconstituting the associated core body, respectively; a screw blockrestrained in axial displacement and adapted to be rotatable relative tosaid center shaft; a longitudinal movement screw member threadedlyengaged with said screw block so as to be restrained in rotation aboutsaid center shaft, and adapted to be axially displaceable; and a linkuniting part for coupling said expanding/contracting link parts to saidlongitudinal movement screw member.
 18. The tire building drum accordingto claim 17, wherein said slider reciprocative driving means are adaptedwith: female screw members coupled to said sliders at radial insidesthereof, respectively; a screw shaft disposed in a hollow of said centershaft and having right and left male screw portions threadedly engagedwith said female screw members, respectively; and screw shaft rotatingmeans for rotating said screw shaft; in which said right and left malescrew portions of said screw shaft have mutually opposite leads,respectively.
 19. The tire building drum according to claim 17, furthercomprising: means for restraining rotation of said screw blocks; andmeans for rotating, together with said sliders, said center shaft fittedthrough said sliders by circumferential convex and concave.
 20. The tirebuilding drum according to claim 17, further comprising: means forrotating both said right and left screw blocks synchronizedly with eachother; and means for fitting said sliders onto said center shaft bycircumferential convex and concave.
 21. The tire building drum accordingto claim 19, further comprising: means for restricting rotation of saidscrew blocks relative to said center shaft.
 22. A tire building methodusing the tire building drum according to claim 1, comprising steps of:locking bead cores by said bead lock means, respectively; then bulging acenter portion of a carcass band while displacing said bead lock meansclose to each other; folding back side portions of the carcass band toradial outsides around the bead cores, respectively; thereafter radiallyexpanding said core body to a maximum diameter, while locking the beadcores; and assembling tire component members onto the radially expandedcore body.
 23. A tire building method using the tire building drumaccording to claim 5, comprising a step of: moving said folding-backarms of said folding-back means to axial insides synchronizedly witheach other, respectively, to synchronizingly swing to radial outsidessaid folding-back arms around proximal ends thereof against swingingforces by said urging means while causing said folding-back rollers tobe rolledly contacted with carcass band side portions, respectively, tothereby fold back the carcass band around the bead cores.
 24. The tirebuilding method according to claim 23, wherein said folding-back armsare synchronizedly swung to radial outsides, respectively, such thatside portions of the carcass band to be folded back by said folding-backmeans are rolledly pressure-jointed to a carcass band center portion byany one of said folding-back rollers at any point of the side portionsof the carcass band.
 25. A tire building method using the tire buildingdrum according to claim 8, comprising a step of: radially expanding saidcore body to a position where at least side surfaces of said core bodyare opposed to the bead cores, respectively, and then folding back thecarcass band side portions around the bead cores, respectively.
 26. Thetire building method according to claim 25, further comprising a stepof: radially expanding said core body to a position where side surfacesof said core body are opposed to the bead cores, respectively, andthereafter displacing said bead lock means to an axial center to bringsaid bead lock means close to core body side surfaces, respectively,thereby starting folding back of the carcass band side portions.
 27. Thetire building method according to claim 26, further comprising a stepof: folding back the carcass band side portions by said folding-backrollers while urging the carcass band side portions toward the carcassband center portion supported by core body side portions.
 28. The tirebuilding method according to claim 25, further comprising a step, afterfolding back the carcass band side portions around the bead cores,respectively, of: pressure-jointing folded back end portions bystitching rollers each subjected to a knurling treatment.
 29. The tirebuilding method according to claim 25, further comprising a step of:gradually reducing a pressure within said center bladder, as an interiorof said center bladder is pressurized to bulge a center portion of thecarcass band and as the core body is radially expanded to a maximumdiameter.
 30. The tire building method according to claim 25, furthercomprising steps of: detecting a load of a motor for driving said sleevereciprocative driving means upon radially expanding said core body; andcontrolling at least one of an internal pressure of the center bladder,and a spacing between said pair of bead lock means, based on a value ofthe load.